1. Field of the Invention
The present invention relates to sound attenuators used in ventilation, and, more particularly, the present invention relates to sound attenuators for positioning adjacent ventilation fans that produce noise and vibration in industrial areas such as mines or factories.
2. Description of the Prior Art
Sound attenuators are used to quiet objectionable high pitched sound and vibrations produced by ventilation fans. Sound attenuators are typically used with axial flow fans such as, for example, those used in underground mining and factories.
One type of conventional sound attenuator comprises concentric tubular inner and outer members having sound absorbing material positioned in a space therebetween. The tubular inner member is made of perforated metal and the tubular outer member is made of solid metal. The tubular members are held in concentric relation by flanges welded between the tubular members at either ends thereof. Although these attenuators provide adequate sound attenuation, they have several drawbacks. They are bulky, heavy, and easily dented and damaged. Since the attenuators are primarily made from metal, they corrode. If the sound absorbing material, which is placed in the space between the concentric tubular members, becomes wet during use, the attenuator is rendered substantially useless and must be replaced.